Thread: Buying a Moisture meter - recommendations?

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Groggy got one of these for around $60 or something. Seemed to think they were ok.
http://profiscale.sieper.com.au/prod...ContContId=179

Anything pinless is going to be hundred$

Pins are going to be more accurate more often then pinless. They all work by measuring the electrical resistance between the two poles... a dud reading from surface contaminants is more likely then a dud reading from inside the wood. That answer will hold true regardless of price point. There are some pretty good pinless ones out there if you're prepared to pay the coin, but they still wont be as accurate as a pinned meter provided its not in the "cheap and nasty" class. Look for one with replaceable pins because you will break them, and remember that because they measure resistance that readings are species dependant. A lot of people think that because their meter says 15% that the wood is at 15% when in fact depending on the electrical resistance of a given species that might be out by 5% or more.

As to brand this is one of those cases where you need to balance two different conflicting ideologies:
(1) You get what you pay for.
and
(2) its irrelevant anyway. Doesn't matter what you use for a moisture meter it's only a guide. See above about the electrical resistance thing because there can be a difference between trees of the same species due to different soil trace elements, age of trees, stresses placed on the tree, etc etc etc. That's why the only method of measuring moisture content that will stand up in a court of law in the event of a dispute is an oven drying test.

FWIW I use a Delmhorst J4.

I have a deltron (Aus made) with handheld pinned probe, wasn't working properly when I got it, (an auction find), I sent it away to be checked, came back with some upgraded circuitry, a test standard (15%) Douglas Fir and a certificate of calibration, I also got a booklet with species and temperature correction figures for Aus. and exotic timbers.
As John G alludes to there's a little more to it than just taking a reading, you need to be sure the meter is reading accurately by testing the meter with the standard and then making the temperature and species corrections after taking the actual reading, you might at least be in the ball park then, otherwise you have a number that may be right but more likely not.



Pete

Originally Posted by pjt

.... came back with a test standard (15%) Douglas Fir and a certificate of calibration.....

.....you need to be sure the meter is reading accurately by testing the meter with the standard.....

Yebbut how do you know that the standard is still at 15%?

Originally Posted by FenceFurniture

Yebbut how do you know that the standard is still at 15%?

A fair question!

The meter measures resistance so inside the test standard (little black box) is a resistor of known value which when placed across the probe pins meter will (should) read 15%. I was curious about this as well so I opened the little black box and that's all that's inside it.

It would then be fair to ask, How do we know the resistor is still at known resistance? I'm not real sure whether resistors change their value, but that can also be measured with an ohm meter and compared with what it should be given the markings on said resistor in the little black box.

And you could also ask, How do we know the ohm meter is reading correctly? and so on and so on until we are asking, Is the colour green the same colour green that I see the same as what you see? or Is gravity really 9.81m/sec 2 (it's an average) or .........



Pete

Ah, I see. I read it that the test standard was a piece of DF at 15%, which would be bound to fluctuate. Even if said piece of DF was kept in a plastic bag there'd be no guarantee of constant % because the most common plastic for bags is Polyethylene which is not really a 100% moisture barrier (but Polypropylene is).

Ah I see how you could read it as such, from what I understand DF is the standard to which all other timbers are compared.



Pete

Ilya bought us one each...dropped it around the other day.

It's great. It was a pinned one on special from Hare Forbes. It was a decent price and we saved a bit on postage.

It also has a resistor test of known value.

So everyone knows, resistors are very accurate things. The little colored bands determine the resistance in ohms, the variance +/- as a percentage, voltages, over limits, etc. If its overloaded it degrades at a known rate. Price and quality are determined by manufacturer and may be specified with unbelievable accuracy. I used to design SLI circuits, doodads and other miscellaneous electronic nastiness.

Originally Posted by Evanism

Ilya bought us one each...dropped it around the other day.

It's great. It was a pinned one on special from Hare Forbes. It was a decent price and we saved a bit on postage.

It also has a resistor test of known value.

So everyone knows, resistors are very accurate things. The little colored bands determine the resistance in ohms, the variance +/- as a percentage, voltages, over limits, etc. If its overloaded it degrades at a known rate. Price and quality are determined by manufacturer and may be specified with unbelievable accuracy. I used to design SLI circuits, doodads and other miscellaneous electronic nastiness.

May I ask, what was a "decent" price please.

Allan

Originally Posted by Allan at Wallan

May I ask, what was a "decent" price please.

Allan

$39 on special ($49.50 regular) plus a half share in post from H+F: http://www.machineryhouse.com.au/W6455

About six months ago I bought a cheapy moisture meter from McJing's. It seems to work OK, and the readings made sense. A mate who has recently retired from a working life in the timber industry really rubbished my cheapy buy. He owns a professional grade moisture meter worth heaps, and believes that any cheapy meter will be useless. So, we did some comparison readings - his professional meter against my cheapy meter. On samples where the timber was still fairly wet, there was a four or five percent difference between the two meters (i.e. 20% versus 25%). But when it came to testing a piece of timber that was almost ready to use (i.e. less than 12%), the two meters read within +- 1%.

I've since done some calibration tests by using a microwave oven to dry some samples. Again, timber that was still fairly green gave readings with a wide tolerance, with semi-seasoned hoop pine being the worst contender with the cheapy meter giving results between 20% and 50% on repeat readings. Tests on Blackwood, Forest Red Gum, Silky Oak, and Maple Silkwood (all supplied by Mapleman, and some still semi-seasoned) all showed that once the samples was under about 15% the accuracy of the readings from the cheapy moisture meter was pretty good. At least good enough for me as a final Go/NoGo check on whether a piece of timber is dry enough to use in a project.

That doesn't mean that all cheapy meters are accurate, but maybe there is less difference between expensive and cheap moisture meters.

Regards,

Roy